1. Technical Field
The present invention relates to a reticulate electrode bus connection, and particularly to a novel guide for attaching a wire bus connection to a reticulate electrode. The present invention is particularly applicable to attaching a wire bus connection to a reticulate cathode for an electrochemical cell or a battery.
2. Description of the Prior Art
Reticulate electrodes are well known and disclosed in numerous prior patents and publications. The common dictionary definition of the term "reticulate" is resembling a net or network having a plurality of crossing fibers. A reticulate electrode is a form of "high surface area" or "flow-through" electrode. In use, the electrode is immersed in an electrolytic solution of an electrochemical cell or battery. Reticulate electrodes are particularly useful with dilute electrolytic solutions because they provide more surface area for the capture of ions in the solutions. The electrodes are "flow-through" in the sense that they have an interconnected open-cell structure through which the electrolytic solution flows.
Prior U.S. Pat. No. 4,515,672, assigned to the assignee of the present application, discloses reticulate electrodes and methods for making them. The reticulate electrodes are made from an open cell polymer foam such as a polyurethane foam which has been made conductive, for instance by coating with carbon particles. The conductive foams typically have a resistivity in the range of about 50-500 ohm-cm, a pore size in the range of about 10 ppi (pores per inch) to about 100 ppi, the pores ranging from about 2 mm to about 0.15 mm in diameter, and a void fraction in the range of about 0.5 to about 0.98. The conductive foams are in the shape of a parallelepiped having a thickness which may range from about 0.2 inch to about 0.5 inch. The width and height of the foams are arbitrary since the electrodes are adapted for the particular cell box or battery casing with which they are used. The surface area of a conductive foam is substantial. A conductive foam which has a thickness of about 0.25 inch, a width of about 18 inches and a length of about 14.19 inches has a volume of about 63.9 cubic inches. A foam of about 25 ppi of this volume has an active surface area of about 425 square feet.
The conductive foams can be plated with a conductive metal, for instance copper or nickel. The thickness of the metal plating can vary widely. The reticulate electrodes, following plating, may be pyrolyzed to remove the polymer substrate leaving a reticulate metal structure. Alternatively, they may be used without pyrolysis. The reticulate electrodes may or may not be subjected to metal annealing, depending upon application. The disclosure of prior U.S. Pat. No. 4,515,672 is incorporated herein by reference.
Electrically connecting the reticulate electrodes to a battery or electrolytic cell bus has been a substantial problem in the art. It is necessary for any connection to have a large area of contact with the reticulate electrode because of the large amount of the current flow through the electrode. In addition to being electrically adequate, the connection must be mechanically strong. Any reduction in the contact area with the reticulate electrode during use can result in the corrosion of component parts. Such corrosion, by way of example, has been experienced with the use of alligator clamps positioned at or just above the air-liquid interface level in a cell or battery.
Prior U.S. Pat. No. 4,515,672 discloses one mode of connecting a reticulate electrode to a battery or cell bus. A support comprises a solid metal plate which overlies the entire surface area of at least one face of the reticulate electrode. The plate is affixed to the reticulate electrode by a plurality of staples, pins or other fastening means. A connector tab protrudes upwardly from the support plate to provide a convenient connection with the battery or cell bus. The support plate is provided with apertures through which the cell electrolyte or solution ions can flow.
Prior U.S. Pat. No. 4,399,020 discloses reticulate electrodes and their use in electrochemical cells and batteries. This patent also discloses methods for the manufacture of the reticulate electrodes. As with the disclosure of U.S. Pat. No. 4,515,672, the disclosure of U.S. Pat. No. 4,399,020 is incorporated herein by reference.
The '020 patent discloses contact bars with extensions which serve as a means for electrical connection with the electrode bus bar. The contact bars are formed of U-shaped galvanized sheet metal. They are secured to a reticulate electrode by slipping them over the upper edge of the electrode and pinching or pressing the sheets together at selected areas along the length of the electrode. A wire lead extends between the electrode bus bar and the contact bar extensions.
Prior application Ser. No. 308,907, entitled "Reticulate Electrode and Cell for Recovery of Metals From Waste Waters", assigned to the assignee of the present application, discloses the use of reticulate cathodes in an electrolytic cell. The reticulate cathodes extend across the width of the cell and seat in aligned vertical slots on the inside of side walls of the cell. The cell is provided with elongated anode and cathode bus bars adjacent the upper edges of the cell side walls. Each bus bar has a plurality of bus terminals spaced along the bus bar. The cathode bus terminals are aligned with the cathode slots. A hook-shaped wire connector pin extends between each reticulate cathode and its cathode bus terminal. At the hook end, the connector pin can seat within a hole in the bus terminal. The bus terminal is externally threaded. A lock nut threaded onto the bus terminal is turned to press the connector pin hook end against the bus bar. An advantage of the cathode assembly of prior application Ser. No. 308,907 is that it provides excellent electrical connection between the reticulate cathode and the connector pin. In addition, the assembly provides a high resistance against accidental separation of the reticulate cathode and the connector pin. The disclosure of prior application Ser. No. 308,907 is also incorporated herein by reference.